Dehydration of glucose using homogeneous and heterogeneous acid catalysts
Abstract
A simple kinetic model has been developed to describe the dehydration of glucose to 5-(hydroxymethyl)-furfural (HMF) and its further rehydration to levulinic acid in the presence of sulfuric acid catalyst. Absorbance measurements in the UV region of 200-320 nm indicated the presence of a kinetic intermediate (I) between glucose and HMF. Preliminary experiments starting with HMF and glucose respectively in acid solution indicated that two side products, D$\sb1$ and D$\sb2$, had to be incorporated in the model. These were modeled as being formed from I and HMF respectively. The five individual reactions comprising the model were each modeled as irreversible first order reactions. Individual rate constants were estimated from batch experiments run under different conditions of temperature and acid concentration. The Arrhenius model and the theory of acid catalysis of hydration (and dehydration) reactions were used to incorporate the effects of temperature and acid concentration respectively on the rates of the individual reactions. The model was then used together with Pontryagin's minimum principle to explore the possilbility of finding optimal operating conditions for the formation of levulinic acid. Zeolite catalysts are known to be good acid catalysts. However, there have been few reports on the use of zeolites in carbohydrate systems. Batch experiments with zeolites indicate that these catalysts can be effective in controlling product selectivity in this system.
Degree
Ph.D.
Advisors
Tsao, Purdue University.
Subject Area
Chemical engineering
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